Cobalt based alloy, article made from said alloy and method for making same

Abstract

The invention relates to a cobalt-based alloy having mechanical strength at high temperature, in particular in an oxidizing or corrosive medium, essentially comprising the following elements (the proportions being shown as percentage by weight of the alloy): 26 to 34% Cr, 6 to 12% Ni, 4 to 8% W, 2 to 4% Ta, 0.2 to 0.5% C, less than 3% Fe, less than 1% Si, less than 0.5% Mn and less than 0.1% Zr, the remainder being composed of cobalt and inevitable impurities, the molar ratio of tantalum with respect to carbon being of the order of 0.4 to 1. Application to articles which are mechanically stressed at high temperature, in particular articles which. can be used for the preparation or the conversion or glass under hot conditions.

1 . Cobalt-based alloy having mechanical strength at high temperature, in particular in an oxidizing or corrosive medium, essentially comprising the following elements (the proportions being shown as percentage by weight of the alloy):  
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   Cr 
                   26 to 34% 
                 
                     
                   Ni 
                   6 to 12% 
                 
                     
                   W 
                   4 to 8% 
                 
                     
                   Ta 
                   2 to 4% 
                 
                     
                   C 
                   0.2 to 0.5% 
                 
                     
                   Fe 
                   less than 3% 
                 
                     
                   Si 
                   less than 1% 
                 
                     
                   Mn 
                   less than 0.5% 
                 
                     
                   Zr 
                   less than 0.1% 
                 
                     
                     
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       the remainder being composed of cobalt and inevitable impurities, 
 the molar ratio of tantalum with respect to carbon being of the order of 0.4 to 1.  
 
     
     
         2 . Alloy according to  claim 1 , in which the proportions of the elements are within the following ranges:  
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   Cr 
                   28 to 32% 
                 
                     
                   Ni 
                   8 to 10% 
                 
                     
                   W 
                   5 to 7% 
                 
                     
                   Ta 
                   2.5 to 3.5% 
                 
                     
                   C 
                   0.3 to 0.45% 
                 
                     
                     
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         3 . Alloy according to  claim 1  or  2 , in which the molar ratio of tantalum with respect to carbon is of the order of 0.45 to 0.9.  
     
     
         4 . Alloy according to  claim 3 , in which the elements are in proportions of the order of:  
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   Cr 
                   29% 
                 
                     
                   Ni 
                   8.5% 
                 
                     
                   C 
                   0.38% 
                 
                     
                   W 
                   5.7% 
                 
                     
                   Ta 
                   2.9% 
                 
                     
                     
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         5 . Alloy according to  claim 1 , in which the elements are in proportions of the order of:  
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   Cr 
                   28% 
                 
                     
                   Ni 
                    8.5% 
                 
                     
                   C 
                    0.22% 
                 
                     
                   W 
                    5.7% 
                 
                     
                   Ta 
                    3% 
                 
                     
                     
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         6 . Alloy according to any one of  claims 1  to  5 , characterized in that it exhibits a non-continuous intergranular phase of carbides.  
     
     
         7 . Article, in particular an article which can be used in particular for the preparation or the conversion, under hot conditions, of glass, made of an alloy according to any one of the preceding claims, in particular by founding.  
     
     
         8 . Article according to  claim 7 , obtained by founding and having been subjected to a heat treatment after casting the alloy.  
     
     
         9 . Article according to any one of  claims 6  to  8 , consisting of a fibre-drawing spinner for the manufacture of mineral wool.  
     
     
         10 . Process or the manufacture of an article according to  claim 8 , comprising the casting of the molten alloy in an appropriate mould and a heat treatment of the moulded article comprising a first annealing at a temperature of 1100 to 1250° C. and a second annealing at a temperature of 850 to 1050° C.